// Licensed to Elasticsearch B.V under one or more agreements.
// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information.

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

#define INTERNAL_NULLABLE_ATTRIBUTES

#pragma warning disable SA1402 // File may only contain a single type
#pragma warning disable SA1649 // File name should match first type name

#if !NETCOREAPP3_1_OR_GREATER && !NETSTANDARD2_1_OR_GREATER || NET461
namespace System.Diagnostics.CodeAnalysis
{
	/// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class AllowNullAttribute : Attribute
	{ }

	/// <summary>Specifies that null is disallowed as an input even if the corresponding type allows it.</summary>
	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class DisallowNullAttribute : Attribute
	{ }

	/// <summary>Specifies that an output may be null even if the corresponding type disallows it.</summary>
	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class MaybeNullAttribute : Attribute
	{ }

	/// <summary>Specifies that an output will not be null even if the corresponding type allows it.</summary>
	[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class NotNullAttribute : Attribute
	{ }

	/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.</summary>
	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class MaybeNullWhenAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified return value condition.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter may be null.
		/// </param>
		public MaybeNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

		/// <summary>Gets the return value condition.</summary>
		public bool ReturnValue { get; }
	}

	/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class NotNullWhenAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified return value condition.</summary>
		/// <param name="returnValue">
		/// The return value condition. If the method returns this value, the associated parameter will not be null.
		/// </param>
		public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

		/// <summary>Gets the return value condition.</summary>
		public bool ReturnValue { get; }
	}

	/// <summary>Specifies that the output will be non-null if the named parameter is non-null.</summary>
	[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class NotNullIfNotNullAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the associated parameter name.</summary>
		/// <param name="parameterName">
		/// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
		/// </param>
		public NotNullIfNotNullAttribute(string parameterName) => ParameterName = parameterName;

		/// <summary>Gets the associated parameter name.</summary>
		public string ParameterName { get; }
	}

	/// <summary>Applied to a method that will never return under any circumstance.</summary>
	[AttributeUsage(AttributeTargets.Method, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class DoesNotReturnAttribute : Attribute
	{ }

	/// <summary>Specifies that the method will not return if the associated Boolean parameter is passed the specified value.</summary>
	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
#if INTERNAL_NULLABLE_ATTRIBUTES
	internal
#else
    public
#endif
		sealed class DoesNotReturnIfAttribute : Attribute
	{
		/// <summary>Initializes the attribute with the specified parameter value.</summary>
		/// <param name="parameterValue">
		/// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
		/// the associated parameter matches this value.
		/// </param>
		public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;

		/// <summary>Gets the condition parameter value.</summary>
		public bool ParameterValue { get; }
	}
}
#endif
